Support relative paths when FTing Schedule:File objects

[shorowit]

Enhancement Request

IDF file paths for, e.g., the Schedule:File object end up as absolute paths after Forward Translation. Users download e.g. ResStock End Use Load Profile models, try to run them, and encounter errors because the absolute file paths don't exist on their computer.

It'd be nice if there was a way to preserve relative paths in the IDF. (As far as I can tell, the OS:External:File object does support relative paths, but they do not get maintained in the final IDF.)

It seems like the implementation could:

1. Add a FT option to use relative paths, or
2. Preserve the OS:External:File path in the IDF Schedule:File (which allows the user to choose if they want to use relative or absolute paths), or
3. ???

I'm not sure if the request applies to other objects.

cc @joseph-robertson